Life Before Fossils (Continued)

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1896.] Life Before Fossils. 279

that law pervades the universe, and although we do not know
as yet the way in which these laws are balanced to produce
all phenomena, that they are so balanced as to produce har-
mony, and that in proportion as the human mind develops it
will be capable of grappling with problems that are not now
within its reach.

LIFE BEFORE FOSSILS.

By Charles Moreis.

(Continued from page 188.)

Such a new stage of existence may have been essayed fre-
quently. The dwellers in the early seas, in their descents
below the surface, must often have come into contact with the
bottom, and at times temporarily rested upon it. This contact
with hard substance doubtless produced some effect upon them,
and certain variations in structure may have proved of advan-
tage in these new circumstances and been retained and further
developed. Particularly if food was found there, and habita-
tion on or near the bottom was tlms encouraged, would such
favoring variations tend to be preserved.

But, as has been said, myriads of years may have passed in
the slow development of swimming pelagic animals before
this phase of evolution was completed. And, perhaps, not
until this was fully accomplished did contact with the bottom
set in train a new series of changes, and in time give rise to
the greatly transformed bottom-dwellers. The change, indeed,
was a great one, if we may judge by the wide diversity in
character between the swimming embryos and the mature
forms of oceanic invertebrates, and must have needed a long
period of contact with the bottom for its completion. Yet it
was probably much more rapid than had been the preceding
pelagic development. Contact with solid substance was a
decided change in condition, and niaj' have greatly increased

280 The American Naturalist. [April,

the preservation of favorable variations. And the area of hab-
itation on the single plane of the sea bottom is so restricted as
compared with that within the many planes of oceanic waters,
that the struggle for place and food must have been greatly
increased, and the development and preservation of newly
adapted forms have been more rapid in consequence.

This may seem to bring us to the very verge of the kingdom
of life as it is known to us from the oldest fossils yet discovered.
Yet in truth we are probably still remote from it. We are
still dealing with soft bodied animals, not with those possessed
of the hard external skeletons from which fossils are produced.
There is no good reason to believe that mere contact with the
earth induced the previously naked swimmers to clothe them-
selves in solid shells. In truth, the earliest bottom-dwellers
may have long continued soft bodied, the hard case or shell
being only slowly evolved. The mantle of the moUusk, for
instance, with its shell-secreting glands, is not likely to have
been a primary accessorj'^ of molluscan organization. The
same may be said of the chitin-forming glands of the Crusta-
cea, and the analogous glandular organs of other types. Such
conditions must have developed slowly, and their appearance
was probably due to an exigency of equally slow unfold-
ment.

For now we come to another highly important problem, that
of the true disposing cause of the development of dermal
skeletons, on which there exists some basis for speculation.
In truth the fossils preserved for us in the Cambrian rocks have
an interesting tale to tell which has a strong bearing upon the
story of animal evolution. And this is, that all these bottom-
dwellers, with the exception of the burrowing annelids, became
covered with what was probably defensive armor. They all
seem to have sought protection in one way or other, and in so
doing became in a measure degenerated forms of life, their
former ease of motion being now partly or wholly lost.

All this represents an interesting stage in the process of
evolution, and indicates some special exigency in life condi-
tions which the animals of that age could only meet by ren-
dering themselves heavy and sluggish with a weight of inclosing

1896.] Life Before Fogdls. 281

armor. This new phase of evolution may have proceeded
very rapidlj^, many forms of early life disappearing, while
those that quiclfly became armored survived.

What was this exigency ? Protection, apparently, as is above
stated. But protection from what? Against what destruc-
tive foe did these ancient animals need such strong defence?
Which among them was the rapacious creature whose ravages
imperilled the existence of all the others? Certainly not the
sponge or the ccelenterate ; they feed on smaller prey. The
mollusk or the echinoderm, in their agile unclad state, may
have been actively predatory, but they were among those
forced to seek protection. Of the known forms the trilobite
seems most likely to have been the aggressive foe in question.
It was the largest, the most abundant, and, perhaps, the most
active of them all, its size and numbers indicating an abun-
dance of easily obtained food, while its great variety of species
points to the existence of varied conditions of food or methods
in food getting.

To all appearances the trilobite was then the lord of life, the
Napoleon of that early empire. Awkward and clumsy as such
a creature would appear now, it was then superior in size,
strength, and probable agility to all other known aniznals,
while its numbers and variety indicate that it was widely dis-
tributed and exposed to all the varying conditions of existence
at that time. What a hurrying and scurrying there must have
been among those small soft creatures to escape this terrible
enemy, from whose assaults nothing seems to have availed them
but an indurated external covering, too hard for its soft jaws-
to master. As the prey became px'otected in this manner the
destroyer probably improved in strength of jaw, and there may
have been a successively more complete growth of protective
devices in the prey and of powers of mastication in the foe.
And thus arose the conditions which first made fossilization
possible, in the development of a series of armor-clad creatures
which were really late comers upon the stage of life, remote as
they seem when measured by our standard of time.

But the story is only half told. The trilobite, as it is known to
us, is under armor also. Not only is it clothed in a dermal
20

282 The Ameriean Naturalist. [April,

skeleton, but, in its later forms, is capable of rolling up into a
hard ball with no part of its body exposed. Evidently the
destroyer himself in time came into peril and needed protec-
tion. Some still more powerful and voracious foe had come
upon the field, and the triumphant trilobite was forced to
acknowledge defeat.

We cannot well imagine any of these animals assuming such
armor except for protective purposes. The weight laid upon
them rendered them slow and sluggish, fixed some of them
immovably, and greatly decreased their powers of foraging.
The only cause which seems sufficient for their assuming this
disadvantageous condition is that of imminent peril — a peril
which afi'ected all known forms alike.

Whence came this peril ? Where is the voracious foe against
whom they all put on armor, even the preceding master of the
seas? No trace of such a creature has been found. In truth,
we cannot fairly expect to find, it, since it was probably desti-
tute of hard parts, and left behind it nothing to.be fossilized.
It had no foe and needed no armor, while lightness and flexi-
bility may have been of such advantage to it that armor would
have proved a hindrance. It probably was a swimming creat-
ure and thus left no impress of its form upon the mud. It is
to this unknown creature that we must ascribe the armored
condition of all known forms of life at that period, even the
later cephalopods, large and powerful mollusks, becoming
clothed in a cumbrous defensive shell, which they were obliged
to drag about with them wherever they went.

It is a strange state of affairs which thus unfolds before our
eyes. All the life we know of seems diligently arming itself
against some terrible enemy, which itself has utterly vanished
and left as the only evidence of its existence this display of
universal dread. The creature in question would appear to
have been without internal or external hard skeleton and with-
out teeth, trusting to indurated jaws for mastication. At a later
date, when its prey became less easily destroyed, teeth may
have developed, and it is possible that we have remains of
them in the hard, cone-like, minute substances found in the
lower Silurian strata, and known as conodonts.

1896.] Life Before Fossils. 283

If we may try and rebuild this vanished beast of prey from
conjecture, aided by collateral evidence, we should consider it
an elongated, flexible form, developed from some swimming
worm-like ancestor, perhaps like the Ascidian embryo, stiff-
ened internally by a cord of firm flesh extending lengthwise
through the body, and moving not by cilia, but by the aid of
fleshy side flaps, the progenitors of the fin. We conjecture it
to have been, in short, the early stage of the fish, a creature
perhaps of considerable size and strength, due to the abund-
ance of easily obtained food, but as destitute of hard parts and
as little likely to be fossilized as Amphioxus.

We may offer this conjecture with some safety, for it is not
long before we come upon actual traces of fish, and of a degree
of development which indicates a long preceding stage of evo-
lution. In fact, the fish in time appears to have been forced
to put on armor, as its prey had earlier done. Internicine war
began in the fish tribe itself. A wide specific variation arose,
with great differences in size and strength, the stronger at-
tacked the weaker species, and eventually two distinct types of
fish appealed, the Elasmobranch and the Ganoid ; the former,
represented to us by the modern sharks, being much the most
powerful and voraciotis, and holding the empire of the open
seas, while the latter dwelt in shallower waters. The Ganoids,
preying on the bottom forms, become themselves the prey of
their strong and active kindred, and, as a result,- the evolution-
ary process just described was resumed. The weaker fish put on
armor, in many cases heavy and cumbrous, a dense bony cov-
ering which must have greatly reduced their nimbleness, but
which safety imperatively demanded. It is these armored
forms that first appear to us as vertebrate fossils ; the first fish,
as the first mollusk or crinoid known to us, being the resultant
of a very long course of development. As regards the Elasmo-
branchs, they, too, became in a measure protected, though not
sufficiently to indicate any very active warfare among them-
selves.

There is little more which we can say in this connection.
The story of the evolution of life bears an analogy worth men-
tioning to that of the development of arms of offense and de-

284 The Ameriean Naturalist. [April,

fense among men. After thousands of years of war with un-
armored bodies, men began to use defensive armor, the body-
becoming more and more covered, until it was completely
clothed in iron mail, and became rigid and sluggish. In the
subsequent period offensive weapons became able to pierce this
iron covering, and it was finally thrown aside as cumbrous and
useless. A similar process is now going on in the case of war
vessels, they being clad in heavy armor, which may yet be ren-
dered useless by the development of cannon of superior pierc-
ing powers, and be discarded in favor of the light and nimble
unarmored ship.

The analogy to animal evolution in this is singularly close.
After long ages of active warfare between naked animals,
defensive armor was assumed by nearly every type of life, ex-
cept the lowest, highly prolific forms, and the highest, which
had no foes to fear. But the powers of offense grew also, and
in time the employment of armor ceased, as no longer avail-
able, its last important instance being that of the ganoid fishes.
The later fish reduced their armor to thin scales, and gained
speed and flexibility in proportion, while in land animals
armor was seldom assumed. In several instances creatures
have gone back to the old idea, as in the armadillo, the porcu-
pine, the turtle, etc., but the thinly clad, agile form has be-
come the rule, armor no longer yielding the benefit that was
derived from, it in the days of weak powers of offense. This
result is a fortunate one, since with increase of agility mental
quickness has come into play, the result being a development
of the mind in place of the old development that was almost
wholly confined to the body. In the highest form of all, that
of man, physical variation has almost ceased, in consequence
of the superior activity of mental evolution.

In conclusion it must be admitted that there are certain for-
mations in nature which seem to militate against the argument
here advanced. I have already spoken of the much questioned
Eozoon canadense. In addition there are the beds of lime-
stone and graphite in the Laurentian formation. But these
prove too much for the advocates of their organic origin. If
so large a fossil as Eozoon had appeared so early, the subse-

1896.] Birds of Neiu Guinea. 285

quent barrenness of the rocks would be incomprehensible.
And had coral animals and large plants capable of producing
such masses of limestone and graphite existed so early, the
absence of any fossils earlier than the Cambrian would be in-
explicable. It is acknowledged, however, that such formations
might have been produced by inorganic agencies, and the facts
strongly indicate that such was their origin, and that fossils
began to be preserved very shortly after the power in animals
to secrete hard skeletons appeared.

BIRDS OF NEW GUINEA (FLY CATCHERS AND
OTHERS).

By G. S. Mead.

{Continued frmn page 196.)

The Thickheads (Pachycephala) are of many species and
scattered widely over the Archipelago. Many have come
under trained observation only during recent years. Prob-
ably many more await discovery.

Pachycephalopsis poliosoma, Gray Thickhead, was discovered
by Mr. A. Goldie in Southeastern New Guinea, and owing to
its distinctive coloration was classed as a new genus. It is
really one of a group of birds which might form a subgenus
and is accordingly so divided by Mr. Gadow. Above the gen-
eral color is dark gray, almost brown, with the head still
darker. The square, rather short tail is also dull of hue. Be-
neath is dull gray, lighter on the abdomen and tail coverts,
whitish to white on the jugulum, throat, chin and side face.
It is a pretty, soft colored little bird about 6 inches long, suffi-
ciently numerous among the mountains of the Astrolabe
range to be called common.

Pachycephala melanura ranges widely over Northern Aus-
tralia and the Archipelago. The general color above is olive-
green ; wing coverts, tail, head and an irregular band passing